The present invention relates to a motor including a stator, a rotor, and a case, which accommodates the stator and the rotor.
Japanese Utility Model Publication No. 5-43749 describes a rotor having the so-called permanent magnet field Lundell type structure that is known as a rotor used in a motor. The Lundell type structure rotor includes two rotor cores and a field magnet located between the two rotor cores in an axial direction of the rotor. Each of the rotor cores includes claw poles arranged in the circumferential direction of the rotor. In the Lundell type structure rotor, the claw poles alternately function as different magnetic poles.
Japanese Laid-Open Patent Publication No. 2012-115085 describes a Lundell type structure rotor including interpole magnets located between alternately located claw poles. The interpole magnets adjust a magnetic path and increase the output of the motor. Such a motor includes a case having a cylindrical yoke housing with a closed end and an end frame arranged on one end of the yoke housing. The rotor and the stator are accommodated in the case.
In each of the above-described motors, the yoke housing, which is a magnetic body, is located on one axial end of the rotor in the axial direction. The end frame, which is formed from a resin, is located on the other axial end of the rotor. In this structure, some of the magnetic flux from a field magnet of the rotor may leak toward the case (yoke housing) and adversely affect the output characteristics.